Negative Spacer Lithography for Nanoscale Contacts and Vias

Spacer lithography has been used to define lines of ultra-narrow width (down to 6 nm) at sub-wavelength pitches [1]. The use of chemical vapor deposition to create a spacer hard mask around a sacrificial material, which is then removed, allows for very good control of thickness and reduced line edge roughness compared with conventional means. In this work, we extend spacer lithography to produce negative features, such as contact holes and trenches. By adding a planarization step following the deposition of a sacrificial spacer, we have demonstrated trenches down to 20 nm of width. It is believed that multiple steps in combination will enable very small contact holes.